Chromecast & bubbleupnp

New to smart things but loving playing so far.

I have managed to get TTS notifications playing throughout the house through mediarenderer connect and bubbleupnp installed on an old Lenovo tab 2.

It reliabily works to use the local renderer on the tablet (i.e. the inbuilt speakers) but I can only get it to autocast when I manually toggle the autocast button.

Does anyone have a solution?

Also is there a way to get TTS notifications to repeat or to be followed up by a siren?